Macromolecular agents composed of serum albumin or linear polymers have MRI contrast enhancement factors less than those predicted for rigid molecules of comparable size. MRI contrast agents based upon dendrimers obviate this deficiency. Terminal primary amines of dendrimers modified with appropriate chelating agents that effectively complex Gd(III) complexes are developed in our laboratories. These reagents possess a molar relaxivity of up to 6 times that of Gd(III)DTPA. Excellent conventional whole body MR imaging and 3D T-O-F MR angiograms have been obtained. Studies continue to thoroughly explore the utility of these agents. These macromolecular chelate conjugated dendrimer based Gd(III) MR contrast agents can be tuned for various applications by adjusting tuning several fundamental criteria: generation (MW & size), core elements (lipophilicity & charge), PEG conjugation, lysine co-administration (renal clearance), and conjugation to targetng vectors (molecular targeting). PAMAM based agents have imaged murine tumor vasculature accurately at the 200 micron scale. DAB based agents have selective properties wherein reverse contrast images of 0.3 mm metastatic liver tumors are detected. These agents can be selectively targeted, not only by conjugation to antibodies, but by other vectors to deliver exceptionally high levels of Gd(III) into disseminated intraperitoneal ovarian cancer tumor. Recent results include: (1) assessment of chemotherapy induced renal toxicity whereby the MRI images of damaged kidney correlate with standard blood chemistries; (2) imaging of the lymphatic system with particular attention to involvement of the lymph nodes relating to lymphoma; (3) imaging of breast cancer involvement with drainage to sentinal nodes for lymph node involvement diagnosis; and (4) effects of external beam radiation on then integrity of tumor vasculature.